The corrections minister is accusing prison staff of risking public safety, after it was revealed dangerous prisoners were being transported on public flights.
Anne Tolley took aim on Twitter yesterday, suggesting that union officials who voiced safety misgivings about the flights were electioneering.
She said it was "inconceivable" that they were not aware of the system, which the ministry claims has been in place for decades.
Ms Tolley also accused prison staff or their union of risking the public's safety by informing The Dominion Post about the flights.
"This is inexcusable. The transportation of prisoners . . . was jeopardised when details were provided to the media," she said later in a statement.
But the Corrections Association said that the department was creating the risk to public safety with its secret flights.
Association president Beven Hanlon said that despite repeated inquiries among prison officers, none was aware of the flights until late last year.
"If Ms Tolley is so confident [that they had been running for decades], she should produce the numbers."
Yesterday, The Dominion Post quoted sources who said maximum-security prisoners from Rimutaka Prison in Upper Hutt had started being transferred on public Air New Zealand flights just before Christmas.
Prison staff said that the department had been putting the "worst of the worst" violent offenders in with other passengers, risking the safety of the public and staff.
There had been at least four transfers of dangerous inmates over a month and another two in the past week. Each prisoner was cuffed and escorted by at least three uniformed guards.
In response, the department said maximum-security prisoners had been transported "on rare occasions" on public flights for decades and there had been no change in policy.
Labour's corrections spokeswoman, Jacinda Ardern, said that the department was not giving a "clear picture" of the situation.
As far as she was aware, Labour was never informed of the air travel system when the party was in government. "Something has obviously changed and we need some answers."
While in opposition, National MPs had attacked their Labour counterparts over the cost of transporting prisoners and it was possible the Government had decided public flights were cheaper, she said.
"It suggests that savings are coming before real risk assessment."
In Australia, the New South Wales prison officers union advised that high-risk prisoners were never transported on public flights.
Steve McMahon, chairman of the NSW prison officers vocational branch, said all prisoners were transferred in vans and, on rare occasions, chartered flights.
"It is not in the public interest for us to have to restrain a person in the middle of a commercial flight."
Despite venting on Twitter, Ms Tolley was not available to speak to The Dominion Post yesterday.
In a statement, she said Labour was wrong and maximum-security prisoners had been transported on public flights when that party was in government.
Suggestions that using public flights was a cost-cutting measure were "absolute rubbish".
Neither Ms Tolley or the department would comment yesterday on how many maximum-security prisoners had been transported using public flights.
- The Dominion Post
What do you make of the proposed conference centre/hotel for Wellington?Related story: Convention centre to get OK